Re: Dive! Dive! Dive!

[Jeffrey Martz <martz@holly.ColoState.EDU>]

Roger Stephenson wrote:
 
> While the elephant doesn't skip like a stone it does not slam into
> the ground and stick like a Tiger Woods approach shot. Inertia happens, and
> just watch the train try to "spike" itself in "The Fugitive". Skidding,
> unless friction was greater during the Cretaceous, happened. The very vast
> difference in body style makes such comparison almost useless any way.
> Tyrannosaurus rex was much more streamlined than any extant large land
> animal.

     The point is that the downward directed impact for a five tonne 
animal is much greater that for that of a smaller animal.  Physical 
resiliancy to impacts does not increase linearly with an increase in body 
size.  You can thicken bone to a certain degree, but bone has its 
limits.  To cite the old saying: drop a mouse off a five story 
building and it will walk away, a human will be broken, a horse will 
splash.       
     In what way is T.rex being "streamlined" going to reduce its mass 
or the damage caused when it hits the ground?    

> Trackway evidence was presented on the Paleoworld episode Dr. Lockley
> appeared on of a large predatory dinosaur "disturbing" a herd of smaller
> dinosaurs, suggesting a chase. Notice I said suggesting a chase in my
> origional posting. I don't know where this trackway is, write Paleoworld if
> you want.
> The Denver MHN Hadrosaur with a Tyrannosaurid bite in its tail is evidence
> of predation on a species capable of sustained herd speed travel and very
> likely much faster when threatened. Trackway evidence for the Hadrosaurians
> is pretty well documented if I'm not mistaken.  

      How fast are the speeds derived from these trackways?  How fast does 
sustained herd speed travel have to be?  How much faster is "much faster"?
      Assuming that T.rex is indeed a predator, why assume that the 
big potential prey animals of its time were so speedy?  T.rex had 
legs significantly longer than the ceratopsians and duckbills of 
its time, which were also massive enough for falling to have been a 
danger.  The relatively short metatarsals (compared to its other 
leg bones) has been cited as an indication that it couldn't run very 
quickly, and it probably wouldn't need to: duckbills and ceratopsians had 
even shorter metatarsals, and had shorter strides as well.           

> Unaddressed in the paper is unknown neck strength, reaction time, skull
> flex, and a other attributes of Tyrannosaurus rex we just don't know yet.
> Dr. Falrow's calculations, as detailed as they are, cannot model the
> aspects I cite.

      I don't think you aprreciate just how powerful the 
type of impact forces we are discussing are relative to the tensile 
strength of bone and muscle.  Unless T.rex made the switch to light 
weight titanium alloy, tensing up its neck muscles or getting a little 
flexion in its skull isn't going to do much to counteract the impact. 

> repeatedly mentioned there is not fossil evidence to firm up either side of
> this coin. Just about anything that has ever lived can make some sort of
> error in judgement leading to death, but how often does it happen aside
> from humans? Even earthworms have self preservation behaviors hardwired.

     Regulating speed so as not to have a potentially fatal accident 
would be a good self-preservation behavior.
     In summary: 
     1. You haven't noted exactly why Dr. Farlow's caluculations 
regarding mass and the forces of impact at a given speed might be in 
error.
     2.  You haven't said exactly why you think T.rex's prey animals 
would be so incredibly speedy.
     3.  You haven't proposed any sort of "safety device" that could 
counteract the force of impact: what sort of things are we 
talking about?  A huge airbag?  An anti-gravity device?       
     
> The reason I dispacted such a strongly worded posting prior to this was not
> so much the material but the tone of the reference to my stand on this
> matter. Suggesting my line of thinking is out of touch with reality
> deserves it, considering the existing physical evidence. Igonore what you
> want, if it makes your beer fizz, but don't expect me to be a whipping boy.

     I'm not expecting you to be a whipping boy.  I'm simply suggesting that 
your oppositions to Dr. Farlow's arguments are not on very stable or well 
evidenced ground.  As far as the lack "physical evidence" in the form 
of broken necked tyrannosaurs is concerned, why are you so certain this 
is due to the impossibility of a falling T.rex being killed rather than 
T.rexs generally not running so fast that falling was a major cause of 
death?  T.rex being careful to moderate its speed could explain the 
lack of broken necked T.rexs as well as T.rex somehow altering the laws of 
physics, and is probably more plausible.     

> Trying not to go ballistic,

     Aren't we all?

LN Jeff
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